Mariner&#39;s compass.



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MARINBRS GOMPASS. y AiJPLIGATIoN FILED MN5, 1914. l 191 10,318D Patented Sept. 15,1914.

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M. B. FIELD 6r, D. RENFRBW.

MABINBRS COMPASS.

APPLICATION FILED JAN. 5, 1914. 1,1 10,318. y Patented Sept. 15,1914.

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' MAVRINERS COMPASS. APBLICA'TION FILED JAN..5, 1914. 1 1 1 0,31 8. Patented sept. 15, '19111 5 SHEETS-SHEET 3.

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1,1 10,318. .Patented sept. 15,1914.

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` Uorzaa Renfreea M. B. FIELD & D. RENFREW.

MARINERS COMPASS.

'APPLIOATION FILED 11111.51914- 1,1 10,318.. Patented sept. 15, 1914.

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'S7/mw@ I e l i free/vif MICHAEL B. FIELD AND DONAL BENFREW, OF GLASGOW, SCOTLAND.

MARINERS contrase.

Specification of Letters Patent.

Patented sept. 15, 1914.

Application led January 5, 1914. Serial No. 810,486.

To all vw71 om. it may concern.

Be it known that we, MICHAEL Bini` FIELD and Donau) RENrnEw, subjects of the King of the United Kingdom of Great Britain and Ireland, both residing at 16, 18, and 20 Cambridge street, Glasgow. Scotland.l have invented a certain new and useful lmprovement in l\lariners Compasses, of which the following 's a specification.

The primary object of the present invention is to provide as an adjunct to a mariners compass an optical system adapted to be supported independently of the compass bowl, and capable of use when the binnacle hood is in place though not liable to. interfere with the convenient removability of said hood, the said optical system being adapted to present an image, in a plane approximately normal to the line of sight, of the lubber point and of a substantial segment of the compass card, in such a manner that, while the helmsman can read the card graduations in the neighborhood of the hibber point to a nicety, he is able to determine the general orientation of the card. these results being obtained in a more effective manner than has been possible by any of the various arrangements proposed heretofore.

Other objects will appear from the following description.

In the accompanying drawings, Figure 1 is a longitudinal vertical section of a binnacle top equipped with an optical system designed to realize the objects of the invention; Figs. 2 and 3 show modifications; Fig. 4 shows part of a compass card which has no reversed markings and which may be employed in a compass equipped with the said optical system; Figs. 5 and 6 show ty ical images presented to the observer by t e optical system.

Referring to Fig. 1, the optical system shown comprises a lens 1 and two reieotors, in the particular instance two mirrors 2 and 3, either or both of which may be angularly adjustable, said system being mounted independently of the compass bowl 4 in which are contained the horizontally disposed lubber mark 5 and card 6.l The lens 1 receives rays which leave the card 6 on its upper side. The mirror 2 in turn receives the rays from the lens 1 and reflects them on to the mirror 3 whence they pass to the eye of the observer; said mirror 3 bein located in a plane inclined to the vertica With this arrangement the image presented to the observers eye will appear as the representation of asubstantial segment of the compas's'card 6 and of the lubber mark 5 standing in an approximately vertical plane and disposed in relation to one another in the same way as the actual lubber mark 5 is disposed in relation to the actual card 6 as viewed when steering directly rom'the card so that the helmsman will have no sense o awkwardness in steering with the combination of compass and optical system.

As will be understood, with the employment of the optical system shown it lis possible to employ a card without reversed markings of any description, so that the card may be simplified, and the points of the card brought near te the periphery so as to be visible with the cardinal, quadrantal and other letterings on the magnified image. It is thus possible to avoid liability to confusion when the card is being read direct, or

read in conjunction with an azimuth mirror.

The mirror 2 is located so as not to obstruct the view of the observer looking approximately horizontally into the mirror 3, c. g., it may be located at a higher level than -the mirror 3 and disposed at an inclination to the horizontal within a darkened chamber 7 in optical communication with the interior of the removable hood or helmet 8.

The interior of the hood 8 up to the aperture opening into the darkened chamber 7 is painted white to provide greater illumination of the compass bowl and card, and at the lubber mark yside. of the hood is a glazed aperture 9 provided with an adjustable cover plate 9 adapted to permit daylight to be thrown on the card vfrom the lubber mark side, the hood being also provided with an inspection aperture 10 serving to permit a full Vview of the card from the helmsmans position when situate-d near the binnacle. The chamber 7 is painted black so as to absorb any stray light and as far as possible to confine the illumination to what passes through the lens 1 on to the mirror 2.

The lens 1 and mirrors 2 and 3 are preferably of rectangular form or of the form represented by the image shown in Fig. 5 and are so disposed in the chamber 7 that the helmsman looking into said chamber 7 will see the image of part of the card and the lubber mark as a detached picture lying in a vertical or approximately vertical plane and not necessarily embraced by a frame and quite independent of the view of the completey card as seen through the inspection aperture. As a protection against reflections the 'lens 1 is sunk in a tube 1f leading to the chamber 7. An inclined glass 13 is also placed in front of the mirrors 2 and 3 and sunk within a darkened casing 12,

the glass 13 serving as a protection against ingress of spray, dust etc., and the underface of said casing 12 being inclined so that water etc., will not collect therein.

It will be appreciated that on removal of the hood 8 the optical system is removed at the same time, thereby leaving the bowl 4 free for the fitting thereupon of an azimuth mirror or shadow-pin device for the purpose of taking bearings.

The compass may be artificially lit from below the card or from the side.

ln the modification illustrated in Fig. 2 the mirror 3X viewed by the observer is located external to the binnacle, and may be fixed above the binnacle, being provided with a deep shade` this arrangement being equivalent to division of the darkened chamber T into two compartments.

As shown in Fig. 2, the lubber mark 5 is so disposed relatively to the lens that the rays leaving the lubber mark 5 and falling on the lens and mirror 2X are approximately Nnormal to the lubber mark.

In the form illustrated in Fig. 3 the optical system employed includes a lens 1-v and a single mirror "23, said lens and mirror being located in a darkened chamber similar `to that provided in the form first above described. Obviously the image viewed by the observer in the mirror 23 will be the reverse of the card, rendering it necessary or desirable to provide the card with reversed mark-- ings It will be understood that the constructions above described permit of the use of magnifying means of such focal length as to bc capable of being placed sufficiently .remote from the card that, while suflicient magnification is insured, the degree of magnification and clearness of the image will not be appreciably affected b v any relativ-e motion between the bowl and the binnaele 4which is likely to occur in practice.

It is an important advantage of the present invention that it provides for the presentation of an image of such a substantial .segment of the card as will fully satisfy requirements wit-hout sacrifice ot compactness. whereas with arrangements supported b v the compass bowl which is mounted on gimbals the use of reflectors of sufiicient dimensions would be impracticable. Animage such as is represented in Figs. 5 and 6 being presented to the helmsman as located in a vertical or approximately vertical plane. may be read by the helmsman with out difficulty even when at a distance greater than was previously feasible. In practice it is found possible for an .observer to read the card to a degree even when stationed ten or twelve feet from the binnacle, whereas, to read a horizontally disposed card, the observer must be fairly near to the card itself, because it cannot be read advantageously when the line of sight is but slightly inclined to the plane of the card.

It will be observed that the optical system employed dispenses with the use of a screen on which an image is projected as in eompasses of the projector' type, the magnifier employed being used practically in the same way as a reading glass, that is, in general, the focal length of the magnifier being greater than its distance from the object to be magnified. Provided the card receives suflicient illumination, whether that of daylight or artificially produced, the image will be sufficiently illuminated: the present arrangement is thus further differentiated from the optical arrangements employed with Compasses of the projector type which require the use of a transparent Card through which the light is transmitted.

lVhile we have, described the forms of construction preferred, it will be understood that the details may be widely Varied without departure from the spirit of the invention.

lVhat we claim is 1. The combination with a mariners compass comprising a bowl containing a card and a lubber mark, of a removable hood sui-mounting the bowl, a. darkened chamber in optical communication with the interior of said hood and an optical system including magnifying and reflecting means for presenting to the observer looking into said chamber an image of said lubber mark and part of said card.

Q. The combination with a mariners compass comprising a bowl containing a card and a lubber mark of a removable binnarlc hood sunnounting the bowl, a darkened chamber having an aperture, said chamber being sustained by said hood and in optical communication with the interior of said hood, and an optiral system inelnding magnifying and reflecting means for presentation of an image of part of said card, said image being visible through said aperture.

3. In combination with a mariners compass comprising a bowl containing a card and a lubber mark. a binnacle hood having an aperture for inspection of the lubber mark and the entire compass card, a darkened chamber in optical communication with the interior of the said hood, said chamber having an aperture, and an optical system including reflecting means Within said chamber for reflecting through said aperture an image of the lubber mark and part of the compass card.

4. In combination with a mariners comclosure includin pass comprising a bowl containing a card, aj closure for the upper end of said bowl, said two chambers the wall of one of which 1s light and the wall of the other of which chambers is dark, said chambers being in optical communication with one another, and said second chamber having an aperture, and optical devices for .A f presenting an image visible through said aperture of part of said card.

5. The combination with a compass binnacle hood having an aperture for inspection of the compass card of a chamber supported by said hood, Said chamber having an aperture, and an optical system including magnifying and reflecting means, said reflecting means being contained within said chamber and ada ted to present an image of part of said car said image being visible through the aperture in said chamber.

6. rllhe combination with a mariners compass com rising a bowl containing a card and a lub ermark, of a removable binnacle hood surmounting the bowl, a chamber having an aperture, said chamber being sustalned b and in optical communication with sai hood, and an optical system 'including a reflector within said chamber for presenting an ima e of art of said card, said image being vlsible t rough said aperture.

7. The combination with a mariners compa comprising a bowl containing a card, of a binnacle hood surmounting the bowl, a darkened chamber having an aperture, said chamber bein in optical communication with thef'interlor of said hood, and two reiectors within said chamber for receiving `and reiecting through said aperture an image of part of said card.

In testimony whereof we have signed our names to this specication in the presence of two subscribin witnesses.

L. B. FIELD. DONALD RENFREW.

Witnesses:

WALLACE CRANs'roN FAIRWnATrmn, HENRY MAscN. 

